1. Field of the Invention
There are many industrial applications in which it is necessary to hold irregularly shaped parts in a relatively precise position in order to allow further machining operations to be done upon the workpiece or for the purpose of supporting it during some further assembly type of operation. Such a holding unit is commonly referred to as a jig, fixture device or a clamp.
A common workbench vise consists of two parallel jaws which can be caused to squeeze a mechanical part, thus holding it rigidly. Such a device has certain limitations. It cannot readily grip parts of arbitrary shape and unless the entire vise is rotated, it cannot grip parts at arbitrary angles.
For some applications, it is desirable that these limitations be overcome. In particular, for the application of mechanical assembly methods by means of an industrial robot or manipulator, it is highly desirable that the robot's work area be provided with a highly versatile vise because such a vise would eliminate the need for otherwise having a large number of highly specialized vises and other holding fixtures. The herein disclosed vise is particularly well adapted for use with a mechanical robot; however, the concept involved can also be utilized in other applications and need not be restricted to automated assembly processes.
2. Prior Art
There have been a number of prior art devices which were developed for the purpose of holding irregularly shaped objects for such purposes as machining operations. These have included means for mounting a specimen in a thermoplastic material as exemplified by U.S. Pat. No. 3,319,289 of J. B. McCormick entitled "Apparatus For Mounting A Specimen", which issued May 16, 1967. U.S. Pat. No. 3,574,257 of DuBois et al, entitled "Automatic Cutting of a Substrate Coated with Thin Layers", issued Apr. 13, 1971, discloses freezing a substrate for the purpose of holding same for subsequent machining operations.
U.S. Pat. No. 3,197,682 of D. L. Klass et al, entitled "Safe Electro-Responsive-Fluid Chuck", issued July 27, 1965, utilizes the Winslow effect wherein the part to be clamped is immersed in a fluid which is subject to an intense alternating electric field to thus increase viscosity of the fluid holding the workpiece. Simple electromagnets have also been utilized to hold irregularly shaped necessarily ferromagnetic workpieces.
U.S. Pat. No. 3,660,949 of Coes, Jr. entitled "Work Holder for Irregular Shaped Workpieces", issued May 9, 1972, discloses a magnetic clutch type of holding apparatus wherein ferromagnetic pellets are fluidized with air pressure and a workpiece inserted therein. Then, the air pressure is turned off and a strong electromagnetic field is applied which rigidizes or solidifies the ferromagnetic pellets thus clamping the workpiece for desired operations.
The above-disclosed devices suffer from a number of problems such as either being quite slow to set up, they undesirably wet or contaminate the workpiece or, in the case of the magnetic system, usually leave some degree of remanent magnetization where ferromagnetic materials are included in the workpiece thus possibly interfering with subsequent use of the part.